The present invention relates to a unique hinge arrangement to be used in a microwave oven having an up-opening door. Microwave heating appliances have gained popularity in recent years, particularly in commercial food operations such as in restaurants and hospitals. It is especially desirable in such use to provide an oven with a cooking cavity which is extended in width such that more than one food item may be cooked simultaneously. With such an oven, an oven door hinged at its side edge is impractical because when it is opened, too much of the counter space in front of the oven will be obstructed. Downward opening doors are not preferred for the same reason and also because an operator may be tempted to place items on the door when loading and unloading the oven, thus possibly impairing the radiation sealing characteristics of the door.
A door designed to open upwardly, however, necessarily would be required to open through an angle significantly greater than 90.degree.. This is because most microwave ovens will be placed on a counter top at waist level and if the oven door does not open beyond a horizontal position, access to the cooking cavity of the microwave oven will be substantially impaired.
An additional problem in a commercial food preparation environment has been maintaining the cooking equipment in an extremely clean and sanitary condition. Some hinge arrangements used in the past have been difficult to clean. A "piano" hinge, such as shown in U.S. Pat. Nos. 3,767,884, and 3,544,751, has proved particularly difficult to clean due to the large number of crevices between interfitting hinge parts. U.S. Pat. Nos. 3,736,398 and 3,849,623 illustrate a hinge arrangement in which two individual hinges are mounted on the exterior of the oven cabinet. Such an arrangement is less likely to collect grease but still presents a cleaning problem.
One approach taken to permit easier cleaning of the oven and its associated hinge is illustrated in U.S. Pat. Nos. 3,196,242; 3,846,608; and 3,749,875. These patents show the use of a hidden hinge which has two hinge plates passing through openings in the oven cabinet to allow for a hinge point which is internal to the cabinet. This type of hinge moves the oven door away from the face of the oven cabinet as the door is opened, thus permitting the face of the cabinet to be thoroughly cleaned. Such a hinge arrangement, however, has heretofore been used only with ovens having downwardly opening doors. This is because previous hidden hinges of this type have been limited to approximately 90.degree. arcuate travel and, as discussed above, an up-opening door used with a microwave oven must have a substantial amount of arcuate travel to allow easy access to the cooking cavity.